A device of the above-mentioned type is disclosed, for example, by EP 0 747 866 B. In the solution described there, the sheet to be deposited is transported by feed rollers to the deposit surface or to the surface of the stack. At the end of the deposit surface or the stack which corresponds to the sheet pick-up position of the roller, a gripper is arranged, which presses the leading end of the sheet to be deposited against the deposit surface or the surface of the stack and therefore holds the sheet to be deposited firmly such that it cannot move. The roller then rolls the sheet to be deposited onto the deposit surface or the respective surface of the stack. As the roller returns into its sheet pick-up position, the roller displaces the gripper again into its opening position, in which a new sheet can be pushed with its leading end under the gripper. If, therefore, the roller is located in its sheet pick-up position, the sheets lying loosely on one another would not be secured against slipping. In order to hold the sheets firmly on the deposit surface even during this time, in the case of the known device flexible pressing elements such as brushes or leaf springs are arranged above the sheet stack, against which the sheet stack is pressed from below and which, when a sheet is being deposited, are pushed to the side by the roller moved over the surface of the sheet stack. This solution is relatively complicated, susceptible to faults and needs a relatively great deal of space.
The invention is based on the object of specifying a device of the type mentioned at the beginning which, with simple means, permits fault-free deposition of the individual sheets on the deposit surface or the surface of the stack and firm holding of the deposited sheets on the deposit surface.
According to the invention, this object is achieved in that the stacking mechanism comprises a second roller which is arranged parallel to the first roller and at a radial distance from the latter, can be displaced together with the first roller parallel to the deposit surface and has at least a second belt, one end of which is fixed to the housing close to the second end of the deposit surface and, starting from the fixing point, is led parallel to the deposit surface and around the second roller to a second belt storage means, and in that the sheet guiding means arranged in the roller comprises first and second guide surfaces for the sheets to be deposited.